全文获取类型
收费全文 | 1598篇 |
免费 | 111篇 |
国内免费 | 1篇 |
专业分类
化学 | 1245篇 |
晶体学 | 19篇 |
力学 | 36篇 |
数学 | 72篇 |
物理学 | 338篇 |
出版年
2023年 | 14篇 |
2022年 | 23篇 |
2021年 | 42篇 |
2020年 | 31篇 |
2019年 | 42篇 |
2018年 | 28篇 |
2017年 | 26篇 |
2016年 | 56篇 |
2015年 | 52篇 |
2014年 | 90篇 |
2013年 | 107篇 |
2012年 | 148篇 |
2011年 | 151篇 |
2010年 | 94篇 |
2009年 | 65篇 |
2008年 | 128篇 |
2007年 | 104篇 |
2006年 | 107篇 |
2005年 | 88篇 |
2004年 | 79篇 |
2003年 | 52篇 |
2002年 | 51篇 |
2001年 | 24篇 |
2000年 | 17篇 |
1999年 | 15篇 |
1998年 | 8篇 |
1997年 | 13篇 |
1996年 | 16篇 |
1995年 | 6篇 |
1994年 | 2篇 |
1993年 | 10篇 |
1992年 | 5篇 |
1991年 | 1篇 |
1990年 | 2篇 |
1989年 | 8篇 |
1985年 | 1篇 |
1981年 | 2篇 |
1975年 | 1篇 |
1969年 | 1篇 |
排序方式: 共有1710条查询结果,搜索用时 31 毫秒
11.
12.
13.
Kwak WJ Han CK Chang HW Kim HP Kang SS Son KH 《Chemical & pharmaceutical bulletin》2003,51(3):333-335
A new triterpenoid saponin, loniceroside C was isolated from the aerial parts of Lonicera japonica. Its structure was established to be 3-O-beta-D-glucopyranosyl hederagenin 28-O-alpha-L-rhamnopyranosyl (1-->2)-[beta-D-xylopyranosyl(1-->6)]-beta-D-glucopyranosyl ester by spectroscopic techniques and chemical transformations. Loniceroside C showed in vivo antiinflammatory activity against mouse ear edema provoked by croton oil. 相似文献
14.
Kang HS 《The journal of physical chemistry. A》2005,109(3):478-483
Using density functional theory, we have theoretically studied the formation of neutral lithium-aromatic complexes R-nLi and R-nLi-R, where R is benzene, naphthalene, or pyrene. We first find that the maximum number of lithium atoms n in the complexes increases with the size of R. In addition, pyrene favors the sandwich compound R-4Li-R over R-4Li more than three times that of the corresponding tendency for benzene, strongly suggesting the possible existence of oligomer (R-4Li)x. We have also investigated energetics and band structures of infinite one-dimensional crystals of R-nLi, finding them metallic. Detailed analysis of the electronic structure shows that all these observations are related to the strong electrostatic interaction among the species, which is originated from the charge transfer from Li atoms to the aromatic rings. In addition, it is shown that the pyrene crystal is mechanically stable with respect to deformation. This also suggests the possibility of its existence, which, in turn, holds potential application in lithium storage in respect to its large Li/C ratio. 相似文献
15.
16.
"Click chemistry" 1,3-dipolar cycloaddition between alkynyl 6-carboxyfluorescein (FAM) and azido-labeled single-stranded (ss) DNA was carried out under aqueous conditions to produce FAM-labeled ssDNA in quantitative yield. The FAM-labeled ssDNA was successfully used as a primer to produce DNA sequencing products with single-base resolution in a capillary electrophoresis DNA sequencer with laser-induced fluorescence detection. 相似文献
17.
A one-step chromatographic method capable of separating all isomers of polyethylene glycol (PEG)-growth hormone-releasing factor (GRF) (1-29) conjugates was developed. The unmodified GRF (1-29) and seven different isomers of PEG-GRF (1-29) conjugates were separated by using a simple reversed-phase HPLC method depending on the differences of hydrophobicity due to the number and site of PEG attachment. The PEGylation sites of all isomers of PEG-GRF (1-29) conjugates were identified by determining the molecular masses of the Lys-C digested fragments with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. This study is a first report for the separation of all PEG-conjugate isomers and would be useful for further studies to find the promising conjugate by evaluating biological activity and stability of each isomer. 相似文献
18.
Treatment of [Cp*Rh(H(2)O)(3)](OTf)(2) (1) with Me(3)SiNH-t-Bu in acetone gave a hydroxyl-capped half-cubane [Cp*(3)Rh(3)(mu-OH)(3)(mu(3)-OH)](OTf)(3)(t-BuNH(3)) (2). Slow diffusion of Me(3)SiN(3) in diethyl ether into compound in acetone produced an azido-capped half-cubane [Cp*(3)Rh(3)(mu-N(3))(3)(mu(3)-N(3))](OTf)(2) (3). On the other hand, treating 1 with Me(3)SiN(3) in acetone gave an azido-bridged, dinuclear rhodium(III) complex [Cp*Rh(mu-N(3))(OH(2))](2)(OTf)(2) (4). Complexes 2 and 3 represent the first azido- or hydroxyl-capped, incomplete cubane-type Rh clusters. Under appropriate conditions, complexes 2 and 3 could be converted to complex 4. The structures of all products were determined by X-ray diffraction. 相似文献
19.
K. No Hyun J. Lee Ki M. Park Shim S. Lee Kwan H. Noh Sung K. Kim Ji Y. Lee Jong S. Kim 《Journal of heterocyclic chemistry》2004,41(2):211-219
A series of novel 1,3‐altemate calix[4]arene azacrowns having mono and bis crown ethers on the lower rim of the calix[4]arene framework were synthesized. Solid‐state structures confirmed the three dimensional conformation of compounds 1–3. 相似文献
20.